With the understanding that when the nectar was generated from the churning of the milk ocean they would share it equally, the demigods and the demons brought the snake Vasuki to be used as the rope for the churning rod. By the expert arrangement of the Supreme Lord, the demons held the snake near the mouth, whereas the demigods held the tail of the great snake. 

Then with great endeavor they began pulling the snake back and forth. Because the churning rod, Mandara Mountain, was very heavy and was not held by any support in the water, it sank into the ocean, and in this way the prowess of both the demons and the demigods was vanquished. 

The Supreme Lord then appeared in the form of a tortoise and supported Mandara Mountain on His back. Then the churning resumed with great force. 

As a result of the churning, a huge amount of poison named kalakuta was produced. The Prajapatis, seeing no one else to save them, approached Lord Siva and offered him prayers full of truth. Siva readily agreed to drink all the poison generated by the churning. The goddess Durga, Siva's wife, was not at all disturbed when Lord Siva agreed to drink the poison, for she knew his prowess. Indeed, she expressed her pleasure at This agreement. Then Lord Siva gathered the devastating poison, which was everywhere. He took it in his hand and drank it, and after he drank the poison his neck became bluish. 

A small quantity of the poison dropped from his hands to the ground, and it is because of this poison that there are poisonous snakes, scorpions, toxic plants, and other poisonous things in this world.